Goji 1984 is the hesei Gojira so, I don't see the need of having that specified.
Hesei usually uses ranged attacks so he'd land his heat ray on titanosaurus, while gigan and mecha G would fly over it. Megalon would dig into the ground under the ray and beneath godzilla. Goji would try to hit the flying kaijus only to have titanosaurus attack hime from the front. The two kaiju would wrestle, and fall into unstable ground from megalon's burrows. While falling, goji would would blast titanosaurus, with heat ray, while it was distracted. This would finish the particularly unmemorable kaiju. Megalon would attack goji from behind with bombs, only to be knocked over by a tail swing. Goji goes to finish of megalon, but gigan takes advantage of this and flies right at him buzzsaw activated. During this megalon burrows underground again. Hmm, and cant think of an ending, but i dont know who will win